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Amber is the common name for fossil resin. It occurs in different colours, and is widely used for making jewellery and other ornaments. Although not mineralized, amber is sometimes considered as a gemstone.
Most of the world's amber is in the range of 30–90 million years old. Semi-fossilized resin or sub-fossil amber is called copal. Baltic amber was called 'Freya's tears' by the Norse and the 'tears of the Heliades' by the ancient Greeks.
Amber in geology
Amber is formed from sap coming out of certain trees. The sap soon becomes a sticky gum, and fossilises as amber. The amber can look different depending on its origin, and its later geological history.
To end up as amber, the starting resin must resist decay. Many trees produce resin, but usually it is broken down by physical and biological process. Exposure to weather tends to disintegrate resin, assisted by microorganisms such as bacteria and fungi. For resin to survive long enough to become amber, it must resist such forces, or be produced under conditions that exclude them.
Baltic amber (historically called Prussian amber) is found as irregular nodules in a marine sand, known as blue earth, in the Lower Oligocene strata of Sambia in Kaliningrad Oblast, where it is now systematically mined.
Agathis amber comes from the conifer Agathis, a tree that used to grow over a much wider area.
The resin can contain, in addition to the beautifully preserved plant-structures, remains of insects, spiders, annelids, frogs, crustaceans and other small organisms that became trapped while it was fluid. In most cases the organic structure has disappeared, leaving only a cavity, with perhaps a trace of chitin.
Locations and use
Although amber is found along the shores of a large part of the Baltic Sea and the North Sea, the great amber-producing country is the promontory of Sambia, now part of Russia. About 90% of the world's extractable amber is in the Kaliningrad region of Russia on the Baltic Sea.
Amber is extensively used for beads and other ornaments, and for cigar-holders and the mouth-pieces of pipes. The Amber Room in the Catherine Palace near Saint Petersburg is notable. It is a reproduction of the original Amber Room, destroyed in WWII.
When gradually heated in an oil-bath, amber becomes soft and flexible. Two pieces of amber may be united by smearing the surfaces with linseed oil, heating them, and then pressing them together while hot. Cloudy amber may be made clearer in an oil-bath, as the oil fills the numerous pores to which the turbidity is due. Small fragments, formerly thrown away or used only for varnish, are now used on a large scale in the formation of "ambroid" or "pressed amber". The pieces are carefully heated with exclusion of air and then pressed into one mass by intense hydraulic pressure, the softened amber being forced through holes in a metal plate. As mentioned, the product is extensively used for making cheap jewellery and articles for smoking.
Amber was much valued as an ornamental material in early times.
- The World of Amber A comprehensive website maintained by the Earth Science Department of Emporia State University, Emporia, Kansas (Accessed 29 May 2005)
- Publications on amber inclusions
- Baltic amber information page